It is uncertain whether the hematopoietic deficiency that characterizes human immunodeficiency virus (HIV) infection is due to impaired production of the hematopoietic colony stimulating factors (CSFs). Infection of hematopoietic progenitor cells, suppression induced by HIV antibodies or other proteins, or a combination of these insults. Our broad objectives are to establish which of these pathogenetic mechanisms are most important. The human immunodeficiency virus is tropic for CD4 positive helper/inducer T lymphocytes and monocytes. Depletion and functional impairment of CD4 positive T cells is a hallmark of the disease, while functional defects of monocytes have also been described. T cells are probably the only source of the multi-poietin interleukin 3 (IL-3), a CSF with profound effects on the survival and proliferation of hematopoietic progenitor cells: together with monocytes and bone marrow stromal cells, T cells also produce a second multipoietin, granulocyte- macrophage CSF (GM-CSF). In addition to several CSFs, monocytes produce several monokines such as interleukin 1 (IL-1) and tumor necrosis factor (TNF), important inducers of CSF expression. Specifically, we wish to determine 10 the IL-3 and GM-CSF synthetic capacity of HIV infected patient T cells and established T cell lines after induction with lectins, phorbol esters or IL-1 and T cell receptor crosslinking, and 2) the monokine and CSF synthetic capacity of patient monocytes, and the CSF responsiveness of patient stromal cells to these monokines. for these studies, we will analyze CSF protein expression by bioassay and immunoassay and RNA expression by the Northern technique, RNAse protection analysis and/or in situ hybridization. If impaired IL-3 or GM- CSF synthesis is found, we plan to investigate the mechanism of gene dysregulation in HIV infected T cell lines by analyzing the proteins that bind to defined regulatory regions of IL-3 and GM-CSF genomic clones. We also plan to use highly enriched normal and patient progenitor cells to 3) evaluate the mechanism of action of putative suppressor molecules, and 4) compare their responsiveness to purified recombinant CSFs tested both singly and in combination: these assays will be carried out in the presence or absence of antiviral agents. Our long term aim is to obtain insight into the pathogenesis of the hematopoietic defect in HIV infected patients that will lead to improved management, including an appropriate choice of GSFs that can be used to treat the cytopenias observed in these patients.